Micro-stream Capnography in Non-intubated Lean and Obese Patients With and Without Obstructive Sleep Apnea

The purpose of this study is to compare the accuracy of EtPCO2 measurements taken with a nasal cannula using the Microcap (Oridion Capnography Inc., Needham, MA) micro-stream device and the TG-920 main-stream device (Nihon Kohden, Tokyo, Japan). Three groups of non-intubated, spontaneously breathing patients will be included: 1) lean patients without obstructive sleep apnea (OSA); 2) obese patients without OSA; and 3) obese patients diagnosed with OSA. This latter group has a higher prevalence of oral breathing. Additionally, to test the efficacy of oral guides, we propose to compare the accuracy of EtPCO2 measurements from the Microcap with two different nasal cannulas, one with (Smart CapnoLine PlusTM, Oridion Medical, Jerusalem, Israel) and one without (CapnoLineTM H, Oridion Medical) an oral guide to trap gas expired from the mouth. The TG-920 main-stream system requires its purpose-designed YG-122T cannula so that is the only one that will be tested with the Nihon-Kohden product.